1. Field of the Invention
This invention relates in general to clamp assemblies for securing a piping system to a surface and more particularly to a clamping assembly which is non-metallic yet able to outperform conventional steel U-bolts in corrosive environments.
2. Discussion of the Prior Art
In the art of securing cylindrical members to support surfaces, problems have surfaced and still plague the industry especially when the entire system is exposed to a harsh environment. Various plastics are now used as piping in many applications. Generally, although less expensive, these plastic piping systems cannot withstand the same clamping forces as conventional stainless steel pipe. Common U-bolts have the disadvantage in that they tend to contact the pipe along a relatively narrow line and create a large load at that line. The effect is somewhat similar to subjecting the pipe to the force of a dull knife and failure of the pipe can result. Even if the piping system is stainless steel, it is possible to distort or damage the piping system with improper use of common U-bolts as clamping means.
Consequently the prior art has tried in many ways to provide a clamping system in which the load on the pipe due to securing the U-bolt is minimized. A search of the prior art has revealed the following list of possible relevent patents:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 4,249,759 Heckethorn 2/10/81 4,393,559 Heckethorn et al 7/19/83 4,388,749 Sassak 6/21/83 4,488,334 Goforth 12/18/84 4,934,635 Sherman 6/19/90 5,014,940 Sherman 5/14/91 ______________________________________
These patents all show various clamp assemblies and their components which are used for securing cylindrical members to a support surface. In general, the features disclosed in these patents are different in structure or function when compared to the present invention. Arguably, the closest reference in this array of patents would be the Sherman patent (U.S. Pat. No. 5,014,940). Sherman uses a conventional U-bolt with special cushion. The cushion fits within the semi-circular part of the U-bolt and forms a saddle to receive the pipe to be secured. The cushion is retained by the U-bolt when the U-bolt is tightened and transmits the clamping force from the U-bolt across the full width of its inner surface to the pipe, thereby distributing that load. The present invention has the same objective in mind, i.e., a distribution of the clamp force across the greatest possible surface of the secured pipe. The means to achieve that end, however, are different than those proposed by Sherman in the '940 patent. The present invention does not teach a cushion as does Sherman and has the advantage of reducing the cost of the clamping assembly, yet distributes the load across a relatively large concentric surface of the pipe. Sherman's cushion can have the disadvantage of being cost prohibitive in this very competitive art. The present invention, therefore, addresses the problem solved by Sherman, but at a lesser expense. Further, in Sherman's system, the steel U-bolt and elastomeric cushion have a different chemical compatibility. In the present invention, the U-bolt and saddle are made from injection molded thermoplastic and are chemically compatible.
A further disadvantage of a conventional metal U-bolt can be seen in certain situations involving PVC coated or painted pipes in corrosive environments. The conventional metal U-bolt, when tightened down due to line contact and hardness, may break the coating of the pipe, thereby exposing the pipe directly to the corrosive environment. The present invention has the advantage in this situation of distributing the stress on the pipe evenly due to its interior flat surface. Further, the U-bolt of the present invention is preferably thermoplastic and similar in hardness to the coating or paint used on the pipe, thereby minimizing the abovementioned problems.